Power operated clutch and brake mechanism



Jn. 4, 1938. H. FOR-D 2,104,455

POWR OPERATED CLUTCH AND BRAKE MECHANISM Original Filed July 27, 1932 3 Sheets-Sheet 1 ATTORNEY.

Jan. 4, 193s. H. FORD 2,104,455

,POWER OPERATD CLUTCH AND BRAKE MECHANISM Original Filed July 27, 1932 3 Sheets-Sheet 2 5j. Z5 Z7 44 Jan. 4, 1938. H. FORD 2,104,455

POWER OPERATED CLUTCH AND BRAKE MECHANISM Original Filed July 27, 1932 3 SheeS-Sheet 3 INVENTOR.

` ffm/W7 7M, BY

ATTORNEY.

Patented Winn.. d, w3@

attent PGY/VER UPERATED CLUTCH AND BRAKE IMECHANISM tion of Delaware Application July 27, 1932, Serial No. 625,653 Renewed July 6, 1937 18 Claims.

The object of my invention is to provide a power operated clutch and brake mechanism especially adapted for use in automotive vehicles whereby the manual energy ordinarily required to operate the vehicle clutch and brake pedals will be materially reduced. This device is ordinarily termed a servo-mechanism. The source of power used to operate this mechanism is the vacuum produced in the intake manifold of the vehicle engine, nevertheless, fluid pressure from any other source such as a hydraulic pump, vacuum pump, air pump or electric power may be readily used if desired.

Specifically, my invention comprises an improved vacuum operated cylinder having a piston or diaphragm therein, which piston is connected through a suitable valve with the intake manifold of the engine. This valve is actuated through suitable mechanism by the accelerator pedal of no the vehicle whereby depression of the accelerator shuts off the vacuum and inversely, when the foot is taken oil` the accelerator pedal then the vacuum is in connection with the cylinder and actuates the piston therein. The piston is connected through a novel linkage mechanism with both the brake andthe clutch pedalsof the vehicle whereby under certain conditions movement of the piston through the rst half of its stroke disengages the engine clutch and movement of this piston through the remainder of the stroke applies the vehicle brake while holding the clutch'dsengaged.

In order that the movement of the piston may come to a stop in its intermediate position or as soon as the clutch is thrown out so as not to apply the brake each time the clutch is released, an auxiliary control mechanism is provided which actuates the vacuum valve and closes same as soon as the clutch is released independently of the accelerator pedal. When the brake pedal is depressed this' same valve is opened again which moves the piston further on its stroke to thus apply the brake while keeping the clutch in its disengaged position. Upon the release of the brake pedal the piston returns to its intermediate position and upon subsequent depression of the accelerator pedal returns to its starting position at which time the clutch is engaged and the brakes are released.

The aforementioned arrangement permits what is known as freewheeling, that is, upon the release of the accelerator pedal the clutch is automatically disengaged and upon depression of this pedal the clutch is again engaged. Thus, the driving wheels of the vehicle are disconnected from the Cul engine when decelerating or coasting down hill or when the brakes are applied.

There are times, however, when it is desirable to allow* the clutch to remain engaged While the brake is being applied and further, under some 5 conditions, it is desirable to allow the clutch to remain engaged while the accelerator pedal is relieved so that the frictional resistance of the engine may be used as a brake. This isparticularly desirable in descending long hills where the continued application of the brakes of the vehicle would cause undue Wear and heating thereof.

In order to accomplish this result it would be a simple matter to provide a manual control for the valve in the vacuum supply line. The disadvantage of this device is that when the freewheeling is disconnected in such manner both the brake and the clutch are required to be totally manually operated so that theadvantages of the servo-mechanism cannot be utilized. When it is remembered that the real advantage of providing a servo-operated brake mechanism is that a brake lining having a low coeicient of friction and consequently a Vvery long life may be utilized with such mechanism, whereas such brake lining could not be used if a manual operated brake were provided. For this reason it is desirable that the servo-brake mechanism be in operation at all times and not simply when the freewheeling device is engaged. With my improved device, even when the automatic clutch feature is not being utilized, the servo-mechanism still actuates the brake upon the initial or control movement of the brake pedal.

Still a further object of my invention is to provide a power or servo-operated clutch mechanism which will provide a major portion of the energy required to throw out the clutch when the freewheeling mechanism is not being used. Heretofore, servo-clutch mechanisms have invariably been provided with follow-up mechanisms similar to the follow-up devices used on servo-operated brakes. The disadvantage of such structure is that the clutch cannot be engaged easily or smoothly under certain conditions. My iml proved device differs from this construction in that the servo-member simply spring loads the clutch pedal so that the saine may be manually operated with an extremely light pressure. This function may be better understood when it is brought out that the servo-piston upon the release of the accelerator pedal always moves to its intermediate position and that this piston is connected with the engine clutch by either a positive jaw clutch or by a coil spring so that when the positive jaw clutch is engaged then the downward movement of the piston automatically disengages the clutch without the actuation of the clutch pedal, While when the jaw clutch is disengaged then the downward movement of the piston loads up the spring which `connects it with the clutch so that only an extremely light pedal pressure is required to overcome the resistance of the clutch spring.

Of course, the loading of this servo-spring reduces the torque which the clutch can safely carry but inasmuch as the frictional resistancev or drag of the engine is neverA over tWenty-ve per cent of the torque developed by the engine, only one-fourth the clutch pressure is required to transmit this resistance or braking load. Consequently, a spring pressure equivalent to seventyve per cent of the clutch spring torque may be safely used without reducing the factor of safety of the clutch. Thus, only twenty-five per cent of the work of disengaging the clutch need be done by the operator, which in an ordinary vehicle amounts to a very light pedal pressure.

Still a further object of my invention is to provide aservo-,operated brake mechanism in which the control pedal is preloaded with a relatively heavy spring pressure'. It has been conventional practice for a considerable time to preload the control pedals of servo-brake mechanisms so that the bake will have a denite feel to thereby prevent the accidental instantaneous application of the brake when only a slight application is desirable. Forthis reason it has been customary to provide a spring capable'of resisting a footpedal pressure of fromv fty to seventy-live pounds in order to develop this resistance or feel in the pedal. In all of such installations known to the applicant, the servo-mechanism has been required to overcome this spring resistance before the brake is applied which not only utilizes conslderable of the servo-mechanism power but also requires that this spring tension be manually overcome even when the servo-mechanism fails to operate.

With my improved device I have provided a preloading spring, but have disposed such spring in such a way that the servo-mechanism is not required to overcome the resistance thereof so that the full power of the servo-mechanism is utilized solely in applying the brakes. Still further, in case the servo-mechanism for any reason fails to operate then the manual effort which would ordinarily be used in compressing the preloading spring is used solely to apply the brakes, none of this pressure being utilized to overcome the preloading spring pressure. This is especially1 desirable where a low coefcient brake lining is utilized as the full pedal pressure is required to operate such brakes manually.

With these and other objects in view my invention consists in the arrangement, construction and combination of the various parts of my improved device, as described in the specification, claimed in my claims, and illustrated in the accompanying drawings, in which:

Figure 1 shows a side elevation of my improved device when installed upon an automobile chassis.

Figure 2 shows a plan view of the device shown in Figure l.

Figure 3 shows an enlarged view of the pedal fulcrum and associated parts.

Figure 4 shows a perspective view illustrating somewhat diagrammatically the construction and function of the several pedals and levers 1.15911 -aiosfie .in this device. This is not a truly represensative view but is designed to show the parts diagrammatically, it being taken somewhat along the dotted line 4--4 in Figure 3 with the several levers and associated arms shown in a single plane to better illustrate the construction, and v Figure 5 is a sectional view, taken through the brake control follow-up mechanism.

Referring to the accompanying drawings, and particularly Figure 1, I have shown a dash member III which is supported upon a frame I9 and which forms the rear wall of an engine compartment in a motor vehicle, this vehicle having an engine II disposed therein which is located justv forwardly of the dash I0. Several iloor boards I2 are also provided which separate the engine and drivers compartments. Mounted upon the forward face of the dash and secured thereto in a vertical position, I have provided a cylinder I3 in [which a suitable piston I4 is reciprocally mounted; The piston isconnected to. a piston rod I6 which extends downwardly in a vertical direction to a position somewhat beneath the floor boards of the car.. A valve I5 is fastened to the upper end of the cylinder I3 which valve is connected by a tube I'I Withthe intake manifold. A second tube. I8 connects that portion 0f the cylinder beneath the piston .with the valve I5 whereby thevacuum may draw the piston. downwardly in the cylinder. When the valve I5 is inV its closed position, vacuum in the tube II will cause no movement of the piston, but when the valve is opened then vacuum in the intake manifold will draw-the piston I4 downwardly to the bottom of the cylinder.

Mounted upon the frame I9 of the vehicle I have provided a bracket 20 in which a transverse shaft 2I is secured. Among other things, this shaft 2I is adapted to rotatably mount one end of a power lever 22, the other end of this lever being pivotally connected With` the lower end of the rod I6 whereby reciprocation of this rod will oscillate the lever 22 around the shaft 2|.

Referring now to Figure 4, it will be .seen that I have provided a brake pedal 23, together with a clutch pedal 24, these two pedals being pivotally mounted on the shaft 2l on either side of the lever 22. The brake pedal 23 is forged integrally with a brake operating arm 25 and the clutch pedal is likewise forged integrally with a clutch operating arm 26 so that operation of either of these pedals will actuate the'respective arm.` The lever 22 is formed integrally with a power arm 21.

It will be noted from this ligure that the lever 22 is provided with a cylindrical hub member 6I upon which a sleeve 28 is rotatablymounted. This sleeve is formed integrally with an arm 29, the sleeve ha'ving a plurality of clutch teeth 39 machined in its outer end. 'It will also be noted that a shiftable clutch collar 3I is splined on'the outer end of the hub member 6I which collar is provided with clutch teeth 32 so that by shift ing the collar to the right, as shown in this gure, the arm 29 and the lever 22 will be positively connected together so as to oscillate in both directions as a unit. However, upon shifting the collar 3I to the left, then the sleeve 2B is free to oscillate relative to the lever 22 or' inversely, oscillation of the lever 22 caused by reciprocation of n will be noted that I have provided a, clutch throw-out shaft 34 ywhich extends through the clutch housing of the vehicle engine and which throw-outshaft is provided with a conventional viork '35 which 'coacts with the main clutch of the engine so that oscillation of the shaft 3l will throw out of engagement the engine clutch. One end of the shaft-34 projects out through the side of the transmission and an arm 38 is secured4 thereto, .which arm has a. beam 31 pivotally mounted at its outer end, one end of. which beam entends radially away from the center of the shaft while the other end extends back towards this center. An adjusting screw 3B is threaded into the arm til in position to coact with the inner end of the beam il so that oscillation of the outer end of the beam tl to the left, as shown in Figure 3, will throw out the engine clutch while 4oscillation of said beam to the right will simply pivot the beam around the outer end oi the arm llt. h sheet metal connecting link it connects the outer ends of the beam 3l with the arm it.

From vthe foregoing it will be seen that movement oi the lever it downwardly when the jaw clutch il is engaged will oscillate the arm 2li which will reciprocate the linh lli thereby oscillating the beam ill and shaft it to throw out the engine clutch. However, when the clutchdi is moved to its .disengaged position then oscillation oi' the lever il will simply tension the .spring liti thereby tending to cscillate the arm it. .its the spring til iscapable oi resisting only about sev-I enty-hve per cent oi' the force oi the springs in me man clutch, it will be seen 'met at mis time the engine clutch does not disengage but simply that the spring pressure on the clutch is lessened due to the 'counteracting force oi the spring lill.

Now in order that the engine clutch may be manually disengaged, the arm it is provided-with a tab dii which is in position aligned with the outer end ci the arm it. Consequently, manual oscillation oi the clutch pedal ifi will cause the dit arm @it to oscillate the arm thereby manually throwing out the engine clutch. n relatively weak helical spring di is disposed between the bracket lill and clutch pedal til to return the clutch pedal to its inoperative position when .the operator releases same.

During normal driving oi the vehicle an accelerator pedal which is given the reference numeral .it is normally held in a depressed position. This pedal is connected through a control Y rod with the valve it and returns the valve to its closed position at this time insuring that the piston ill and lever it remain in thmr inoperative positions. When, however, the pedal fili isreleased then the valve it is opened and connects the vacuum-tube i'i'with .the underside oi the piston thereby drawing the piston downwardly so as to cscillate the lever il. When the clutch collar il is in its engaged position the engine clutch is automatically disengaged by this movement, however, Awhen the clutch il is in its disengaged position then uponreleasing I the accelerator pedal the lever 22 still oscillates 'itt but the clutch remains engaged until the clutch pedal it is actually moved by the operators foot. Due to the energy stored up in the spring 88 the movement oi the clutch pedal is accomplished with much less exertion than would be necessary to throw out the main engine clutch without the servo-mechanism. In fact, the

.pedal pressure is reduced to about one-fourthfits,

lieve the vacuum in the cylinder it.

usual amount without lessening the torque which the clutch is capable of transmitting under ordinary driving conditions. As the clutch-pedal pressure is reduced only when the accelerator is f torque of the engine.

Referring now to the brake hook-up, it will be noted that I have provided a rod M which extends forwardly from a main brake cross shaft on the vehicle, and which rod is connected thereto so that movement of this rod in the direction shown by arrow t5 will apply the vehicle brakes. The forward end of the rod it is provided with a clevis dt which slips over a clevised end il. which is formed on the end of the arm it, and a pin it extends through these two clevises so that oscillation oi the arm it will apply the braces. lt will be noted from Figure 5 that the pin till is closely :dtted in the clevis it, however, a relatively large clearance opening it is disposed in the clevis ill so that considerable movement is permitted between the pin it and the clevis lil. The purpose oi this clearance is to provide a limited movement betweenthe arm it and the brake rod dil this movement being used to actuate a control mechanism which in turn operates the servo-device. The pin it is provided with a head til which is aligned with the outer end of the power arm il, and this pin and arm il are in its inoperative position the arm il will not contact with the head td. lit is only after the engine clutch has been thrown `out by movement oi the lever iii that the arm. il strikes against the head t@ so that further movementoi this arm causes the braises to be applied.

Referring to Figure 5, it will be seen that a control beam ti is pivotally secured by means ci a pin b2 to the outer end oi the clevis di. The pin closely tits both the openings kin the clevis and the openings in the beam di so that only pivotoil movement between these two members is permitted. lt will also be noted that the beam di entends down through the` clevis il and is provided with an openingtherethrough aligned with the pin lil which oiwinine.r is proportioned so that an intimate dt is made with this pin. 'While there is clearance between the pin titl and Lthe opening dit in the arm lll. there is no clearance between the pin td and the opening in the beam di. Thus, the beam iii' and clevis di' are linlred together so that relative movement therebetween is prevented. The beam di and clevis dit may thus pivot as a unitaround the pin it and arm it. y

The free end of the beam ti is secured to an operating rod di which extends upwardly where it is secured to an arm lit, the outer end of which is pivotally mounted upon the accelerator shaft; (resiliation oi' the accelerator pedal does'not tmd to move the arm M but the accelerator shsit simply serves as a fulcrum to support this ami. Yan adjusting screw l5 is disposed between the valve4 i5. Consequently, either downward movement of the accelerator pedal or upward movement of the rod 53 will close the valve l! to replunger 51 and beam shown by arrow 59.

It will be noted from Figure 5 that the intermediate portion of the beam 5l is provided with a sleeve 56 screwed therein, this sleeve having a plunger 51 reciprocally mounted in its outer end. A relatively stiff compression spring 58 is interposed between theI plunger 51 and the beam, this spring serving, as will hereinafter be described, to load up the brake pedal. so as to besubstantially aligned with the plunger 51 and the parts are so proportioned that when the power lever 22 reaches an intermediate position along its stroke, or to the position assumed thereby when the clutch is thrown out, then the arm 21 will bear against the plunger 5 1 thus moving the beam 5I around the pivot 52 so as to reciprocate the rod 53 thereby closing the valve l5. The spring 58 possesses sufficient resistance so that as far as this function is concerned the 5I may be considered as a rigid unit., Thus, while 'the engine clutch is held in its disengaged position the arm 21 is being retained in the position shown in Figure 5. It Will further be noted that even though the freewheeling clutch 3l is disengaged so that the engine clutch is not automatically thrown out, upon releasing the accelerator the power lever 22 and arm 21 advance to the position shown in Figure 5 irrespective of the functioning of the engine clutch. Thus, under every condition when it 1s desired to apply the brakes, the arm 21 wili be in the position shown in Figure 5.

If it is now desired to apply the brakes of the car, it is only necessary to depress the foot pedal 23 thereby moving the arm 25 in the direction This action moves the pivot pin 52 in the same direction but there being considerable clearance between the opening Q9 and the pin 48 a direct pull on the clevis 46 is not at this time accomplished. However, if the clevis 46 remains stationary while the pin 52 advances, then the beam 5I must oscillate around the pin 52 to the position shown by dotted lines 68 to thereby draw the rod 53 downwardly thus opening the valve l5. As the arm 21 is in the direct path of such pivotal movement of the beam 5l, the spring 58 must be compressed to complete this movement. This compression can be accomplished solely by the movement of the brake pedal 23. This spring can, of course, be so proportioned that any desired resistance to the movement of the pedal is readily obtainable.

When the valve I 5 is opened by theaforementioned action, then the power lever 22 is forced lstill further downwardly thus moving the arm 21 in the same direction as the arrow 59 so that if the arm 25 is manually moved through say five degrees, then the lever 22 moves through the same five-degree movement thereby forcing the beam 5| back to its former position wherein the valve I5 closes. A further movementof the arm 52 is followed up by the same movement of the arm 21.

Now in order that movement of the lever 22 may apply the brakes, the outer end of the arm 21 is proportioned so as to bear against the head 58 of the pin 48 when the mechanism is in the position shown in Figure 5. However, brake pedal is depressed theopening 49 moves forwardly'in relation to the pin 48 so that the head 58 bears against the end of the arm 21. Consequently, the follow-up movement of the arm 21 directly moves the clevis 46 and rod 44 to thereby apply the vehicle brakes. Thus, the only manual energy required to apply the brakes is that necessary to compress the spring 58.

The arm 21 is offset the arm 25 and clevis 46.

when the `A very important feature in connection with this device is that the lever 22 and arm 21 when they oscillate to apply the brakes, bear directly against the head l50 of the pin 48 so that the servo-mechanism is not required to overcome or compress the spring 58. It is true that the spring 58 must be compressed to start the servo-device but this compression is accomplished solely by the manual force of the operator. This function will be more apparent when it is considered that there is no anchorage for the spring 58 against the frame of the vehicle so that even though it is under compression when the brakes are applied, still this compression cannot in any way work against or detract from the force of the servomechanism.

It is apparent that if for any reason the vacuum of the engine should fail, upon depressing the brake pedal 23, the arm 25 will move in the direction of the arrow 59 thus pivoting the beam 5l around the pivot 52 to position where the pin 48 bears against the rear of the opening i9 at which time a solid connection is made between The arm 21 being at this time in its inoperative position, or that shown in Figure 1, and the vacuum having failed, the plunger 51 will not strike against this arm so that the compression of the spring 58 is not required. Thus, in case the servo-device fails the full energy of the brake applying force is conducted directly to the brake mechanism and no portion thereof is utilized in compressing the preloading spring. This feature is very desirable as a brake lining having a low coefcient of friction may be used and still ample braking efficiency be obtained. I v

Just as an additional safety feature, I have provided a manual control 63 for the valve I5 whereby this valve may be operatively closed to allow the engine, clutch and brake mechanism to oper- I ate exactly as in the conventional car. This control should not be confused with the control for the freewheeling clutch 3l, as the latter, while eliminating the automatic clutch throw out, still retains the servo-operated clutch and brake functions. The control 63 prevents all movement of the servo-mechanism and is designed to be used primarily to contrast the difference in operation between the conventional vehicle and this improved servo-mechanism.

Among the many advantages arising from the use of my improved device it may be well to repeat that I have provided a servo-mechanism of relatively simple and inexpensive construction and in which a single power cylinder is used to both throw out the clutch and to apply the brakes.

Further, that this power cylinder is so arranged that either the clutch or brake can be selectively operated.

Still further, freewheeling is obtained, that is, upon releasing the accelerator pedal the clutch is automatically thrown out.

Still further, when freewheeling. is not desired, the servo-mechanism still materially assists in overcoming the force required to manually throw out the clutch, which feature should be distinguished from the follow-up mechanism ordinarily associated with servo-clutches. These mechanisms, while successfully. throwing out the clutch, still are difficult to operate when engaging the clutch, especially when it is desired to slip the clutch, as in parking the car. With my device the manual control of the clutch pedal is identically the same as is used in the conventional automobile the only difference being that a portion oi the clutch spring pressure is counteracted by the servo-mechanism.

Still further, this device is provided with a preloading spring which produces a feel on the brake pedal and gives the desired` characteristics to the operation of the brake and still the force of thisV sprine is not required to be overcome either by the servo-mechanism or by the brake pedal when the device is manually operated. Consequently, the lull manual or servo-force is utilized in actually applying the braking load.

Some changes may be made in the arrangement, construction and combination of the variber, shiitable means for positively connecting 'the vehicle clutch with said power member whereby actuation of said member will disengage said clutch, said shiitable means being readily shifted to an inoperative position whereby actuation oi said power member will not disengage said clutch,

and resilient means connecting said power member and clutch located so that actuation of said power member when said sl'iiftable member is inoperative will energize said resilient means to thereby partially counteract the force required to manually disengage the vehicle clutch.

2. .a device, as claimed in claim 1, wherein the power actuated member comprises a piston adapted to reciprocate in a cylinder.

3. li device, as claimed in claim l, wherein the power actuated member is operated by the intalre manifold vacuum of the vehicle engine.A

d. il. device, as claimed in claim l, wherein said shiitable means comprises, a law clutch.

5. il. device, as claimed in claim l, wherein said resilient means comprises a. metallic spring. d. .a servodevice adapted to automatically selectively disenaaee or assist in disenpaainp the clutch ola motor vehicle comprisina, a power actuated member, control means operated by the releam oi' the vehicleiaccelerator pedal ior edectine the actuation oi said power mei-t r, shii'tabie means for positively connecting the vehicle clutch with said power member whereby the release ci said accelerator pedal will automatically diseneape said clutch, said shiitable means beine readily shifted to an inoperative position whereby the release of said accelerator pedal will not cauce the disenaagement oi said clutch, and resilient means connectinp said power member and clutch located so that the actuation of said power member when said shiitable member is in-I operative will energizey said resilient means to thereby parti counteract the i'orce required to manually disengage the vehicle clutch only when said accelerator pedal is released.

'i'. iii device, as claimed in claim 6, wherein the power, actuated' member comprises a piston adapted to rcdprocate in a cylinder.r

d. a device, da claimed in claim 6. wherein the power actuated member is operated by the 'intake manifold vacuum ofthe vehicle engine.

d. a device, as claimed in claim 6, wherein the power actuated member is operated lby the intake manifold vacuum of the vehicle engine, and

wherein said control means comprises a valve controilina said vacmnn andl which is opened upon the release of the accelerator pedal.

10. A device, as claimed in claim 6, wherein 'said shiftable means comprises a jaw clutch.

' 11. A device, las claimed in claim 6, wherein said resilient means comprises a. metallic spring.

12. A servo-device adapted to operate the clutch of a motor vehicle comprising, a vacuum operated piston operatively connected to a power lever, whereby reciprocation of said piston will oscillate said lever, an arm adapted to be oscillated to disengage said clutch, said arm and lever being'pivotally mounted in concentric positions, means for operatively clutching said arm. and lever together whereby oscillation of said lever will oscillate said arm to positively disengage said clutch, said clutching means being readily disconnected so that oscillation of said lever will not disengage said clutch, and a spring interposed between said lever and said clutch arm whereby oscillation of said lever will energize said spring when the clutching means is dise connected, to thereby partially counteract the torce required to manually disengage said clutch.

i3.. ln a device, as claimed in claim l2, wherein said clutching means comprises a .jaw clutch splined on said lever and manually shiitable into and out oi' engagement with said ann to thereby connect and disconnnect said lever and arm.

ld. ln a servo-device adapted. to operate the clutch and brake of a vehicle, a power actuated member operatively connected to said clutch and brake so that movement of said member through an initial portion oi' its stroke disengaaes the ve-- hiclc clutch and further movement thereof applies the vehicle brake, shiitable clutching means disposed in the connection between said member and clutch which in its inoperative position allows said member to move through said initial portion of its-stroke without disenpaeinar said clutch, means operated by releasing the vehicle accelerator pedal lor edectinp only said initial movement, and means operated by the vehicle bralre pedal ior edectina the full `movement oi said member to thus apply the brahes, said shittable means permitting the operator to select whether or not the clutch will be automatically disenuased by the releasing oi the accelerator pedal.

l5. .il device, as claimed in claim ld, wherein the power actuated member consists of a vacu-` um operated piston.

lo.. .d device, as claimed in claim la, wherein a resilient means is interposed between said power actuated member and said clutch which when said shiitable means is inoperative is 'stressed by the initial actuation oi the power member to thus counteract a portion oi the spring pressure required to hold the vehicle clutch in engagement only when said accelerator pedal is released.

l?. d servo-device adapted to operate the' clutch and. brakes of a vehicle comprising, a reciprocable 'power actuated member, means connectim said member and the vehicle clutch whereby the initial portion ofv the stroke of said member disengages the vehicle clutch, a brake l is effecting the disengagement of said clutch, said ling device upon the actuation of said power member to apply said brakes, a spring associated with said controlling device which coacts with said arm to urge the controlling device to its inoperative position only when said power member spring resisting the movement of said pedal only when said power member is functioning to apply the brakes.

18. A servo-device adapted to operate the brakes of a vehicle comprising, a power actuated member, an accelerator pedal, means connecting said accelerator pedal and power actuated member whereby said power member is actuated through an initial portion of its stroke by the release of said accelerator pedal, a vehicle clutch, means connecting said clutch and said power actuated member whereby said initial stroke portion disengages the vehicle clutch, a brake pedal,

20 brake linkage extending between said pedal and the brakes ci the vehicle, a controlling device mounted upon said pedal and movable thereon to effect the movement of said power member by the manual application of said brake pedal, means connecting said power member with said brake linkage at a point between the wheel brakes and said controlling device, said last mentioned connecting means having an arm associated therewith which moves relative to said controlling device upon the actuation of said power member to apply said brakes, a spring associated with said controlling device which coacts with said arm to urge the controllingI device to its inoperative position only when said power member has moved from its starting position and only when said power member has disengaged the clutch, said spring resisting the movement of said brake pedal only when said power member is functioning to apply the brakes. 

